Synchronizing system for electronic tubes



May 2, 1953 R. c. MIERENDORF 2,638,566

SYNCHRONIZING SYSTEM FOR ELECTRONIC TUBES Filed Feb. 16, 1951 IN V ENTOR. W? (7 ME/d/Ya rx Patented May 12,- 1953 SYNCHRONIZING SSTEM FORELECTRONIC TUBES Robert G. Mierendorf, Milwaukee, Wis, assignor toSquareD Company, Detroit; 'Mich.,a corporation of Michigan ApplicationFebruary 16, 1951, Serial Ida-211,358

8 Claims.

This invention relates to a circuit for effectin synchronousenergization of an electronic tube.

More specifically, this invention relates to an electrical circuit forcontrolling the energization of an electronic tube in which conductionthrough the electronic tube is always initiated at the beginning of apositive half cycle of anode voltage. One object of the presentinvention is the provision of an improved synchronizing circuit' for anelectronic tube whereby the electronic tube will conduct only full halfcycles of current.

Another object of the present invention is the provision of an improvedelectronic tube initiating circuit operating duction-through thebeginning of a half cycle of positive anode voltage regardless of thepoint on the voltage wave at which the initiating contact may be closed.

Another object of the present invention is the provision of anenergizing circuit for an electronic tube in accordance with thepreceding objects, in which voltages differing in time-phase are appliedto the control and shield grids of the electronic tube to effectenergization of the electronic tube at a particular point on the anodevoltage wave.

Other objects and features of the invention will be readily apparent tothose skilled in the art from the specification and appended drawingillustrating certain preferred embodiments in which the drawing is adiagrammatic representation of an electronic welder circuit in which thepresent invention is incorporated.

In the drawing there is shown a pair of main supply lines 5 and 2, whichare connected to asource of energy, not shown. Disposed across thesesupply lines is a transformer 3 having a secondary 4 which supplies apair of conductors 5- and 6 which electrical energy. Connected acrossthese conductors 5 and 6 is a transformer 1 having a secondary winding 8which is of opposite polarity to the primary of transformer I.

The secondary winding 8 is connected between the conductor 6 and aconductor- 9. In series with each other, and connected between theconductors 6 and 9', are a resistor H and initiating contact l2. To apoint between the resistor H and the contact l2 there is connected oneterminal of a capacitor I3, the other terminal being connected through aresistor 14 to the control grid 15 of an electronic tube 16, which hasan anode ll, a cathode l8, and a shield grid l9. The shield grid 19 isconnected to a junction between the elements of a series cirto effectinitiation of con- 1 electronic tube only at the cuit' which comprises aresistor 2 l and a capacitor 22, this series circuit being disposedbetween the conductors 6 and 9. Also connected to the conductor 9' is aresistor 2.3 which is electrically connected to the control grid 15 ofthe. electronic tube "5' through the resistor hi. Also connected to thecontrol grid I5 is one terminal of a capacitor 24 the other terminalthereof being electrically connected to cathode l8 of tube It.

' Across the conductors 5 and 6 there is disposed a transformer 25having a secondary 26 which serves to supply heat to the cathode l8 ofthe tube ('6.

The anode H of the tube [6 is connected to the conductor 5 through acircuit which comprises a weld-no weld switch 21, which is in serieswith a parallel circuit, one leg of which includes an inductor 28' and acapacitor 29; the other leg includes a relay coil 3| of anelectromagnet. Energization of the relay coil 31 effects movement of amovable contact 32 into position to bridge contacts 33 in the ignitercircuits of a pair of inversely paralleled ignitrons 34 and 35, whichare conventionally disposed between the main supply lines i and 2. Theseignitrons serve to energize a welding transformer 36 in series withtheignitrons across the supply lines, transformer 36 having a secondarywinding 31 across which a pair of welding electrodes 38 are dis posed.

U on connection of the main line conductors l and 2 to a source ofelectrical energy, the transformer 3' will be energized, the transformer3 secondary winding serving to energize transformers I and 25, secondary26 of the latter transformer supplying energy to heat cathode [8. Withthe switch 21' closed, anode voltage will be supplied to the mainelectrodes H and I8 01: thetube It. With the initiating contact 12 inthe position indicated in the drawing, during those half cycles in whichthe anode H of the tube l 6 is driven negative with respect to thecathode t8, current will pass through resistor H, capacitor ('3, andthepath between the control grid [-5 and the cathode it of tube IE tocharge capacitor l3. This current flow through the control grid when theanode is negative is due, of course, to the" fact that secondary 8 is ofa polarity opposite to that of the secondary 4. This chargeon capacitorl3 establishes a D. C. voltage in the control grid circuit of the tube[6 which provides a voltage between the control grid l5" and the cathodel8 of tube It which is negative at all times, except for short periodsduring which anode I1 issubstantially negative with respect 3 to thecathode I8, so that tube It will not conduct. During theseaforementioned short periods, the charge upon capacitor I3 is reestablished by control grid conduction of tube I5.

To the shield grid I9 of the tube I6, there is applied the voltageacross capacitor 22 which slightly lags the voltage of the secondarywinding 8. The shield grid I9 conducts current during the positive halfcycles of voltage applied thereto, and by virtue of the phasedisplacement between the shield grid voltage and the voltage ofsecondary winding 8, the shield grid will remain positive for a shortperiod during which the anode I1 goes positive, the shield grid I9 goingsubstantially negative after this short period and remaining so untilafter the anode II goes negative.

When the initiating contact I2 is closed, further recharging of thecapacitor I3 is prevented, the capacitor I 3 thereby discharging throughresistors 9| and 23, the voltage at the control grid I5 of tube I 6during this discharging period being comprised of the decaying voltageof the capacitor I3, upon which is superimposed a small A. C. voltagedue to current flow through resistors 23 and I 4 and capacitor 24. ThisA. C. voltage component lags the voltage of the secondary winding 8 and,therefore, tends to maintain the control grid i5 positive at thebeginning of a positive half cycle of anode |'I voltage. As the voltageupon capacitor 3 is dissipated, tube I6, therefore, will begin to fireonly during those periods in which the shield grid and the anode areboth positive, these moments occurring only at the beginning of apositive half cycle of anode voltage. If conduction of tube I5 is notinitiated at the beginning of one positive half cycle, the shield gridvoltage, which is substantially negative during the remainder ofthathalf cycle, will prevent firing of the tube until the beginning of thesucceeding positive half cycle of anode voltage, regardless of the factthat the capacitor l3 voltage may be dissipated, and the control gridlose its negative bias, during said one positive half cycle. Assumingthat the switch 21 is closed, tube l6 will then begin to conductcurrent. This current will effect the energization of the coil 3| whichwill, after a predetermined period, effect closure of the movablecontactor 32 upon the fixed contacts 33. One relay of this type which isdesigned to provide substantially transient free weld current initiationby effecting closure of the contacts at approximately the normal currentzero for the associated welder is shown and described in the copendinapplication of Robert C. Mierendorf and Ernest G. Anger, entitledElectro-Magnetic Relay, Serial No. 152,594, filed March 29, 1950. Thisrelay will close the contacts about 240 after the initiation of currentflow through the-energizing coil. It should be noted that this closuretherefore occurs during the half cyclewhich follows the first conductinghalf cycle of tube I6.

Upon closure of the contacts 33, current will flow from the main powerlines to effect ignition of the ignitron having positive anode voltage,

current then flowing from the positive power line through the ignitronto energize welding transformer 35, the secondary 31 thereof effectingcurrent flow through the welding electrodes 38 and the work associatedtherewith. Ignitrons 34 and 35 will continue to conduct successive halfcycles of current until such time as the movable contactor 32 is nolonger bridging the fixed contacts 33.

The circuit paralleling the relay vcoil 3| is so '4 designed as tomaintain the coil 3| energized during those half cycles ofnon-conduction of tube It which follow conducting half cycles. Uponopening of the initiating switch 22, a charge will be reestablished oncapacitor I3 and operation of the tube IE will be interrupted. Duringthe first half cycle of non-conduction of tube I 6, capacitor 29 will,in the conventional manner, be discharged through relay coil 3| tomaintain its energization. Upon the second half cycle of non conduction,the inductor 28, which is chosen to have a value such that thecombination of the inductor 28 and the capacitor 29 are in resonance,will cause a rapid reversal of current flow through the relay coil 3|and consequent rapid deenergizati'on thereof. The contacts 33 willtherefore always be opened during the second half cycle which follows aconducting half cycle of tube I G. This resonated circuit is describedand claimed in the copending application of Ernest G. Anger entitledElectric Control Circuit, Serial No. 148,190, filed March 7, 1950.

' It will readily appear that tube I6 may begin to conduct only upon thebeginning of a positive half cycle of anode voltage and therefore onlyfull half cycles of current wil1 pass through the tube. Current flowthrough relay coil 3| will therefore occur only in full half cycles.Furthermore, as contacts 33 are always closed during the first halfcycle following a conducting half cycle of tube is, and as contacts 33are always opened during the second half cycle following suchconduction, weld current fiow will therefore always be initiated in halfcycles of the same polarity and will be interrupted during half cyclesof opposite polarity. Furthermore, it is obvious that while the featureof the present invention which provides for synchronous start of currentflow through tube I6 has been described in conjunction with theoperation of a Welder circuit, it is equally adapted to use with anycircuit in which it is desirable to obtain only full half cycles ofcurrent flow through the controlling electronic tube.

While certain preferred embodiments of the invention have beenspecifically disclosed, it is understood that the invention is notlimited thereto, as many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

What is claimed is:

1. In a control circuit, an electronic tube having an anode, a cathode,and at least a pair of auixilary electrodes, means for-applying a firstalternating voltage between said anode and cathode, means for applying asecond alternating voltage displaced in phase from said first voltagebetween one of said auxiliary electrodes and said cathode such that saidone auxiliary electrode is positive when said anode begins to gopositive but negative shortly thereafter,

initiating means, voltage establishing means between said cathode andother auxiliary electrode for preventing conduction of said tube untilafter the operation of said initiating means, means for dissipating theeffect of said last mentioned means after the operation of saidinitiating means whereby said tube will begin conducting only during theperiod in which both said anode and said one auxiliary electrode arepositive, and control means responsive to current flow through saidtube.

2. In a control circuit, an electronic tube having an anode, a cathode,and at least a pair of auxiliary electrodes, means for openin a:

alternatingvoltage between said anode an oath ode, means forapplyingasecond alternatin voltage displaced in phase from said first voltagebetween one of said auxiliary electro'desand said cathode which tends tomakesaid tube become conductive during a redeterminedilllltihififibltibfl or a positive half. cycle or anodevoltage and whichprevents conduction or said tubeduring the remainder of the positivehalf cycle, voltage" after the operation of and initiating means wherebysaid tube will begin conducting only during said predetermined portionof a positive half cycle of anode voltage and control means responsiveto current flow through said tube.

3. In a control circuit, an electronic tube havin an anode, a cathode,and at least a pair of auxiliary electrodes, means for applying a firstalternating voltage between said anode and cathode, means for applying asecond alternating voltage displaced in phase from said first voltagebetween one of said auxiliary electrodes and said cathode such that saidone auxiliary electrode is positive when said anode begins to gopositive but negative shortly thereafter, means for establishing adirect voltage between said other auxiliary electrode and said cathodewhereby said other electrode is normally negative to said cathode duringthose periods in which said anode is positive, an initiating switch,means for dissipating said direct voltage after operation of saidinitiating switch whereby said tube will begin to conduct only duringthe period in which said one auxiliary electrode and said anode are bothpositive, and control means responsive to current flow through saidtube.

4. In a control circuit, an electronic tube having an anode, a cathode,and control and shield grids, means for applying a first alternatingvoltage between said anode and cathode, means for applying a. secondalternating voltage displaced in phase from said first voltage betweensaid cathode and shield grid such that said shield grid is positive whensaid anode begins to go positive but negative after said anode has beenpositive for a short interval, initiating means, means for establishinga direct voltage between. said cathode and control grid for preventingconduction of said tube until after operation of said initiating means,means for eliminating the effect of said last mentioned means after theoperation of said initiating means whereby said tube will begin toconduct only during the interval when both said anode and shield gridare positive, and control means responsive to current flow through saidtube. i

5. In a control circuit, an electronic tube having an anode, a cathode,and control and shield grids, means for applying a first alternatingvoltage between said anode and cathode, means for applying a secondalternating voltage displaced in phase from said first voltage betweensaidcathode and shield grid such that said shield'grid is positive whensaid anode begins to go positive but negative after said anode has beenpositive for a short interval, a capacitor, means connecting saidcapacitor to said control grid, means for charging said capacitor with apolarity such that said control grid is negative with respect to saidcathode when said anode is positive, an initiating switch, means fordissipating the charge upon 6, said capacitor after "the operationv "orsaid .lnitiat-' ing" switch whereby said-tube will begin to co both"said duct oniy'during the i ter'val when anode and shield grid arepositive, and contror means responsive to current flow through saidtube.

inga'n anode, a cathode, and control andshield grids, meansiar applyinga first alternating volt-- age between saidanodeand cathode, plying asecond alternating voltage displaced degrees from said first voltage, afirst series circuit' including a first resistor and a first capac'-:itor'connect'e-d across said second voltage, meansconnecting-saidcathode to the terminal-of said: first capacitor spacedfrom said first resistor, means connecting said shield grid betweensaid-- first resistor and said first capacitor, whereby said shield gridvoltage is displaced in phase from said first and second voltages anamount such that said shield grid is positive when said anode begins togo positive but negative after said anode has been positive for a shortinterval, a second series circuit including a second resistor, a secondcapacitor, the control grid and the cathode connected across said secondvoltage, whereby said second capacitor is charged during positive halfcycles of said second voltage, the charge upon said second capacitormaking the control grid negative at all times when the anode ispositive, an initiating switch in parallel with that part of said secondseries circuit which includes said second capacitor, the control gridand the oathode whereby recharging of saidsecond capacitor is preventedafter operation of the initiating switch, means for dissipating thecharge upon said second capacitor after operation of the initiatingswitch whereby the tube will begin to conduct only during the intervalwhen both the anode and shield grid are positive, and control meansresponsive to current flow through the tube.

'7. In a control circuit comprising an electronic tube and meansresponsive to the conduction thereof; an electronic tube having ananode, a cathode, and at least a pair of control electrodes; means forapplying a first alternating voltage between said anode and cathode,initiating means, means for applying a direct voltage between one ofsaid control electrodes and said cathode which prevents conduction ofsaid tube, means for dissipating the effect of said last mentioned meansupon operation of said initiating means, and means for applying avoltage between said other control electrode and said cathode whichmakes said other control electrode positive with respect to said cathodeas said anode becomes positive and which makes said other controlelectrode negative with respect to said cathode a small fraction of ahalf cycle after said anode has become positive, whereby said tube canbegin to conduct only during the initial portion of a half cycle.

8. In a, control circuit comprising an electronic tube and meansresponsive to the conduction thereof, an electronic tube having ananode, a cathode, and at least a pair of control electrodes, means forapplying a first alternating voltage between said anode and cathode,means supplying a second alternating voltage displaced substantially 180degrees from said first voltage, a first series circuit connected acrosssaid second voltage including a first resistor and the first capacitor,means connecting said cathode to the terminal of said first capacitorspaced from said Gain a control circuit, an electronic tube havmeans SUDfirst resistor, means connecting one of said control electrodes betweensaid first resistor and said first capacitor whereby the voltage betweensaid one control electrode and said cathode is displaced in phase fromsaid first and second alternating voltages an amount such that said oneof said control electrodes is positive when the anode begins to gopositive but negative after said anode has been positive for a vsmallportion of' a half cycle; a second series circuit connected across saidsecond alternating voltage including a second resistor, -a secondcapacitor, the other of said control electrodes and said cathode; saidsecond capacitor being charged during positive half cycles of saidsecond alternating voltage, said other control electrode being madenegative when said anode is positive by said charge on said secondcapacitor; an initiating switch in parallel with that part of secondseries circuit which includes said second capacitor, the other of saidcontrol electrodes and said cathode, whereby recharging of said secondcapacitor is prevented after operation of said initiating switch; andmeans for discharging the charge upon said secondcapacitor afteroperation of said initiating means whereby the tube will begin toconduct only during the interval when both the anode and said onecontrol electrode are positive.

7 ROBERT C. MIERENDORF.

References Cited in the file Of this patent UNITED STATES PATENTS NumberName Date 2,359,080 Bivens Sept. 26, 1944 2,463,318 Schneider Mar. 1,1949

